I have a pitched roof 1900 house that has had no insulation in the attic. We have a full floor to walk on and electricity up there, so we'd like to make it habitable for a rough play/schoolroom. I am planning on putting baffles and cotton/denim batts between the rafters and on exterior walls. I was going to leave it at that without putting up drywall, since the insulation is safe to touch, unlike the fiberglass. My question is: do I need to install a vapor barrier. The cotton insulation is supposedly treated to avoid mildew, etc. and by keeping it open (without drywall), air would be circulating around it easily. I should mention I do have soffit and ridge vents. If I can avoid a vapor barrier, I'd prefer it. What do you all think? Thanks!